Cordless pool cleaning robot

ABSTRACT

A cleaning robot for a swimming pool has a body unit with a battery power pack, adapted to move along the floor and/or walls of the pool. The robot may comprise a tail portion adapted for floating on the surface of the pool. The tail portion may have a float user interface. The robot may have a memory adapted to store a certain orientation of the robot and a controller to align the robot&#39;s orientation in accordance with the stored orientation. The robot may further be adapted to perform straight and stepped laps, to move in known mutually angled directions independently of the swimming pool&#39;s shape. The robot may perform a plurality of cleaning modes.

FIELD OF THE INVENTION

This invention relates to devices and methods for cleaning swimmingpools, basins, and the like. More particularly, the invention relates toan automatic self-propelled cleaning robot powered by electricalrechargeable batteries.

BACKGROUND OF THE INVENTION

Battery powered pool cleaning robots are known in the art. They provideseveral advantages over robots that are powered via a power cable. Themost apparent is that the cord is susceptible to entanglement as therobot makes the turns and rotations associated with normal scanning of apool.

However, a battery operated robot has the limitation that the timeneeded for the robot to finish the entire scanning procedure is limitedto the time the battery can power it between charges. In a regular(rectangular) pool, scanning the pool's floor is often performedaccording to the following algorithm: a robot traverses the pool flooruntil first encountering a sidewall; it then retreats from the sidewallin a direction perpendicular thereto, travels a predetermined distance,and rotates through 90 degrees; the robot further proceeds untilencountering the next sidewall, and repeats the process until a certainnumber of 90-degree rotations has taken place; the predetermineddistance is then increased and the entire procedure is continued untilthe scanning time is over, or until the predetermined distance equalshalf the distance of a full traversal of the pool. This results inCartesian-like scanning, where the robot moves along two directions thatare perpendicular to each other.

In an irregularly shaped pool, the above scanning algorithm will notresult in Cartesian-like scanning. For example, when used in acircular-like pool, the robot adapted to perform such a scanningalgorithm will mostly move in radial directions, due to which the centerof the pool will be scanned more often than anywhere else, whilst it islikely that its periphery will not be scanned completely within the timeallowed by the battery life.

A number of suggestions have been made for battery operated poolcleaning robots, which attempt to mitigate the limitation of a limitedbattery life. U.S. Pat. No. 4,962,559 discloses a self-containedcordless electric pool and spa cleaner, which is maneuverable over bothflat and highly contoured underwater surfaces. A pump impeller poweredby an electric motor is used to draw water through a filter cartridge.The efficiency of the filter cartridge is said to be designed so as toallow for the use of a small motor and small battery which, in turn,result in the small size of the cleaner. All electrical components areenclosed in a watertight chamber so as to allow the entire cleaner to besubmerged under water.

U.S. Pat. No. 5,507,058 discloses a self-powered apparatus forautomatically cleaning submerged surfaces, such as the floor and sidewalls of a swimming pool. The apparatus includes onboard sensors and anonboard processor (preferably, a microprocessor) which controlsoperation of the apparatus in response to status information suppliedfrom the sensors. The apparatus has an onboard watertight battery and anadjustable inlet nozzle size, and includes left and right track treadswhich are controllable to cause the apparatus to turn or rotate(clockwise or counterclockwise), or translate in a forward or reversedirection, on a horizontal or vertically inclined submerged surface. Theapparatus includes Hall effect transducers (with associated permanentmagnets) and a microprocessor mounted within a sealed control assembly.The microprocessor is programmed to execute a selected one of a numberof cleaning programs (thereby entering a selected operating mode) inresponse to exposure of the Hall effect transducers to a magneticallypermeable card punched with specially arranged holes, or a card with amagnetically permeable insert molded within it.

U.S. Pat. No. 5,454,129 discloses a self-powered pool cleaner withremote controlled capabilities. The cleaner includes a head having alower base in a generally rectangular configuration with side openingsextending vertically therethrough and an enlarged leading edge. The headalso includes an intermediate cover positionable over the base with acentral aperture extending therethrough with an apertured peripheralflange and a gasket positionable between the flange and the base. Alsoincluded is a top cover positionable over the intermediate cover andbase for constituting a plenum zone. The top cover includes an aperturefor coupling to a suction hose and an antennae extending upwardlytherefrom. A brush is peripherally positionable downwardly from thelower face of the base. Parallel axles extending transversely throughthe base with drive wheels on one of the axles. Steering wheels arepivotally coupled to others of the axles with a steering rod forpivoting the wheels to change directions. A drive motor is within thehousing to rotate the drive wheels. A steering motor is provided foraxially shifting the steering rods. A receiver is within the base todrive the steering motor in one direction or another in response tosignals from the antennae and receiver.

SUMMARY OF THE INVENTION

The present invention relates to a pool cleaning robot powered by atleast one rechargeable battery and being free, during use, of any cablesconnected to an external power supply. The robot comprises a robot bodywith one or more batteries, a main controller, at least one brush, adrive means, a water inlet and outlet, an impeller, and a filter.

In accordance with one aspect of the present invention, the robot isprovided with a tail unit comprising a head portion adapted to float atthe surface of the pool, and a tethering cable, which is connected atone end to the head portion and at another end to the robot body, atleast when the latter is in use. The tail unit may comprise a tailcontroller and a float user interface at the head portion. The tailcontroller may be in communication with the main controller in the robotbody via the tethering cable, and may be electrically connected to thebatteries.

The float user interface may comprise at least one status indicator,communications port, and a power socket. The at least one indicator maybe adapted to report the status of the filter, the battery, or whetherthe unit is on or off. The communications port may be used to downloaddata from an external computer in order to update the software on themain or tail controller. It may also be used to upload diagnostic datafrom the robot. The power socket may be adapted to be connected to anexternal power source for charging the batteries or to power the robot,when desired.

The robot may be designed for connection to an external battery charger,with a charging cable to be connected to the tail unit to charge thebatteries in the body unit of the robot. The charger may communicatewith the main and tail controllers, and may have a charger userinterface to display status information on one or more data presentationunits in addition to or instead of the status indicator on the floatuser interface.

In accordance with other aspects of the present invention, the robot maybe provided with one or more measures to facilitate completion of itsscanning operation within the time allowed by the batteries betweencharges. One of the above measures is that the robot may bepre-programmed to stop at or near a sidewall of the swimming pool, inorder to facilitate easy removal of the robot from the pool, e.g. bymeans of its tail unit. The robot may be adapted to proceed to a walland stop upon determining that either an abnormal or a normalpre-determined condition has been met.

Another measure to facilitate completion of the robot's scanning is aselection of a least power-consuming wall detection mechanism. This maybe accomplished by monitoring the electrical load on the drive means,alone or in combination with the use of a sensor such as a tilt sensor,or other mechanical device. Such monitoring is particularly useful whenthe vertical sidewalls of the pool are such that conventional climbingbecomes impossible for the robot, such as when they are covered withalgae or are made of an especially smooth material.

Still other measures are special scanning algorithms, that may bedesigned to ensure efficient, e.g. Cartesian-like, scanning ofarbitrarily shaped pools. Also, there may be provided a possibility ofselection of different modes and/or parameters of scanning operations.

In accordance with further aspects of the present invention, methods ofoperating the robot having the above features are provided.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carriedout in practice, specific embodiments will now be described, by way ofnon-limiting examples only, with reference to the accompanying drawings,in which:

FIG. 1 is a partial cut-away perspective view of a robot according toone embodiment of the present invention;

FIG. 2 is a partial cut-away perspective view of a tail unit of therobot shown in FIG. 1;

FIG. 3 is a perspective view of an external battery charger for a robot,such as shown in FIG. 1;

FIGS. 4A and 4B are block diagrams representing, respectively,operational relationships between the robot body shown in FIG. 1 and thetail unit shown in FIG. 2, and between the latter unit and the batterycharger, such as shown in FIG. 3;

FIG. 5A is an illustration of typical non-Cartesian-like scanning in anirregularly shaped pool; and

FIG. 5B is an illustration of Cartesian-like scanning method in anirregularly shaped pool, in accordance with one embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an example of a robot 1 in accordance with one embodimentof the present invention. It comprises a robot body unit 10 and anoptional tail unit 22. The robot body unit 10 comprises a battery pack12, brushes 14, a drive means with a motor 16 and tracks 17 connectingthe motor to the ends of the brushes 14, and a water outlet 19. Not seenin FIG. 1 are a water inlet, an impeller, a filter and a maincontroller, which are housed within a housing 18 of the robot and areknown per se. The main controller may be a chip protected from exposureto water and comprising a memory and a processor. In addition, the robotcomprises a handle 20 which contains two floats for maintaining abalanced position during use on a pool's floor, and a diagonal positionwhen cleaning at the waterline. The battery pack 12 is enclosed within asealed compartment.

During operation, the impeller draws water from the floor or sidewall ofthe pool via the water inlet through the filter. The clean water isexpelled through the water outlet. In addition to facilitating thecleaning of the pool, this process provides the force which keeps therobot against the pool surface. This is generally similar to theoperation of known externally powered robots such as the one marketedunder the name Dolphin by Maytronics, Ltd., Israel, except that thepower source for the robot 1 is the internal battery pack 12 instead ofexternal power delivered via a power cable.

Standard scanning may comprise cleaning the pool floor with or withoutascending a sidewall. Cleaning with ascending the sidewall is wellknown, and one variation is described in U.S. Pat. No. 6,099,658 (U.S.'658). The robot 1 may ascend vertical sidewalls in order to clean themand the waterline, either according to a standard procedure, such asdescribed in U.S. '658 columns 3-4, whose description is incorporatedherein by reference, or with a novel -method of the present invention,which will be described herein.

The tail unit 22 is shown in more detail in FIG. 2, and it comprises ahead portion 24 adapted to float on water, and a tethering cable 26,which is attached to the head portion 24 at its one end, and to therobot body unit 10 at its other end. The head portion 24 is shown tohave a conical shape body 28 converging, when in use, downwardly, i.e.toward the pool floor, and a top portion 30 adapted to float at or abovethe surface of the water. The tethering cable 26 may be detachable fromthe robot body unit 10, but, at least in use, remains attached and is ofsufficient length to allow the head portion 24 to float near the surfaceof the deepest water in swimming pools for which the robot is designed.It may be suggested that the length of the cable 26 does not exceed 1¼times the maximal depth of a standard pool. For example, the length ofthe tethering cable 26 may be between 2.25 and 2.5 meters. The tail unit22 further comprises one or more counterweights 32, adapted to maintainthe floating working position of the tail unit during use. The headportion 24 may further comprise a float user interface 34 and a tailcontroller, which may be a microprocessor.

The head portion 24 is preferably designed to avoid entanglement withany obstacles. For this purpose, it may have a round cross-sectionalshape at least in the area of its top portion to move easily aroundobstacles such as grip handles, traps, and ladder rails. In addition,the tail unit 22 is sealed against water entry, which allows it to divebelow the water when encountering obstacles such as floating lane ropes,allowing for free continuous operation. The diving is accomplished bythe shape of the head portion 24. When the head portion 24 encounters anobstacle on the surface of the water, the robot body unit 10 continuesoperation, pulling the tethering cable 26. When the tethering cable 26becomes taut, the head portion 24 slides below the surface of the waterto circumvent the obstacle.

The head portion 24 of the tail unit 22 has a float user interface 34which may comprise one or more data presentation units 38. These unitsmay be lights or light emitting diodes, controlled by a tail controller(not seen in FIG. 2) to indicate, for example, the unit power status(On/Off). The float user interface 34 may further comprise at least onesocket 40, that is sealable and adapted to receive external connections.These external connections may include, but are not limited to, acharging cable and/or a communications cable, which can be used todownload software updates to the controller and upload diagnostic datafrom the robot's main controller. The user interface may furthercomprise a power switch 42. In order to enable many of theaforementioned functions, the tail controller is in communication withthe robot's main controller via an integrated communications cable inthe tether cable 26.

The float user interface 34 furrier comprises an antenna 36 adapted toreceive commands from a wireless remote control unit. This remotecontrol unit may be adapted to perform different functions, includingone or more of the following:

-   -   choose the mode of cleaning operation of the robot;    -   cause the robot to move hi a direction directed by a user and        independent of scanning algorithm;    -   predetermine the cycle time; and    -   select the length of a pool to be scanned.

The robot 1 may be provided an external battery charger 44 shown in FIG.3. The charger 44 comprises an external cable 46 adapted for connectingto an external power source, and a charging cable 48 adapted forconnecting to the socket(s) 40 of the head portion 24 for charging therobot 1. In addition, the charger 44 and the tail unit 22 communicatevia the charging cable 48. The charger may further comprise a chargeruser interface 50 and an On/Off switch 52. The charger user interface 50may comprise one or more data presentation units 54. These units may belights or light emitting diodes, to be during charging to indicate thestatus charging and the status of one or more parameters of the robot.These parameters may include, but are not limited to, filter status andbattery status. The charger user interface 50 may further comprise areset switch 56, which is used to reset the main controller's filtermonitoring when the filter is cleaned or changed. Some or all of theelements described in reference to the charger user interface 50 mayoptionally be located on the float user interface 34.

FIGS. 4A and 4B illustrate a block diagram of the main and tailcontroller, and of the battery charger, and elements of the robot towhich they are related. The block diagram of FIG. 4B is an expansion ofthe block labeled “Robot” in FIG. 4A. The block diagram isself-explanatory and, therefore, no detailed description thereof will beprovided.

The tail unit 22 is preferably adapted for raising thereby the robotbody unit 10 from the floor of the pool to the surface. To make surethat this is easily achievable, the robot may be pre-programmed toterminate operation, when necessary, near a sidewall so that the tailunit 22 floats within the grasp of a person standing outside the pool.The robot may be pre-programmed to terminate operation when at least oneof several normal or abnormal conditions occurs. These conditions may bethat no or little more useful scanning can take place, due to, forexample, the completion of the scanning procedure, or the fact that thebattery power or voltage has dropped below a predetermined threshold, orthe fact that the filter is covered with retentate to the extent that nomore useful filtering can be accomplished. The tail unit 22, whenconnected to the charger 44, may be designed to display which conditionhas been met. Alternatively, the robot may stop after a predeterminednumber of wall detections have occurred once the at least one conditionis met.

The tail controller may be adapted to monitor the battery chargingprocess and to allow for full battery charging while disconnectingpower-consuming components, minimizing unnecessary use of power. It maydetect overheating conditions during charging and protects the batteryfrom over-discharge. It also may maintain a minimum power consumptionwhen the robot is not involved in a cleaning cycle. In this way, certaincomponents of the robot, such as data presentation units, will stillfunction even after the cleaning cycle has completed.

The main controller may be preprogrammed to perform scanning accordingto one of several algorithms. Ideally, when a swimming pool is scanned,its entire floor area should be scanned without, or with a minimal,overlap so as to perform the scanning in the shortest time. Based onthis, the efficiency of robots for cleaning swimming pools is evaluatedby measuring the time it takes the robot to completely scan a givenswimming pool.

As mentioned before, scanning of swimming pools may be eitherCartesian-like or non-Cartesian. A Cartesian-like scanning pattern inwhich robot moves mostly in two mutually perpendicular directions, isknown to be obtained in rectilinear pools with four mutuallyperpendicular walls, with a conventional scanning algorithm, asdescribed in the Background of the Invention.

The same conventional algorithm, however, results in anon-Cartesian-like scanning pattern when used in a pool of anon-rectangular shape as illustrated in FIG. 5A. In it, the robot startsfrom a location S1 and travels in a straight line until it detects awall at point W1, then it retreats from the wall in a direction that isgenerally perpendicular to the tangent thereto at the point of impactand it travels for a predetermined time T, after which it rotatesthrough a 90 degree angle at point R, and travels in this directionuntil the next wall detection occurs at point W2. The robot then repeatsthis procedure until a predetermined number of wall detections hasoccurred, after which the time T is increased. Since in an arbitrarilyshaped pool, the walls form arbitrary angles with adjacent walls, thedirections in which the robot will retreat from the wall after differentwall detections are likely to be completely different from one another,resulting in a non-uniform scanning of the pool. For example, asillustrated in FIG. 5A, in a circular or oval pool, most of directionsin which a robot is bounced from the pool's walls are radial, i.e. pass.through the pool's center. Thus, in such a pool, the area close to thepool's center will be scanned more often than areas closer to the poolperimeter, whereby no uniform scanning may be achieved, and no efficientpower consumption may be obtained.

In view of the above, the procedure may be provided, in accordance withone of the aspects of the present invention, to allow Cartesian-likescanning of an irregularly shaped pool, as illustrated in FIG. 5B. Toperform this procedure, the robot body unit 10 is provided with a meansknown per se for detecting its orientation. Such means may be, forexample, in the form of a digital compass integrated onto the maincontroller in the robot body unit 10. Once the robot 10 is located inthe swimming pool to be scanned, the absolute orientation thereof ismeasured and stored as a reference orientation. This orientation may bethat of the direction of travel of the robot in relation to magneticnorth. With reference to FIG. 5B the robot then moves along, keeping itsoriginal orientation from a starting location S2 until it first impactsa wall of the pool at point W3. It then retreats from the wall in adirection that is perpendicular to the tangent thereto at the point ofimpact, as in standard cleaning procedures. In accordance with one ofthe aspects of the present invention, the robot subsequently rotates atpoint R1 until it is realigned with the reference orientation.Subsequently, the realignment will take place upon every wall detectionto orient the robot to move parallel to the direction in which it movedat the reference orientation, or to move perpendicularly to thedirection it moved with the reference orientation.

In particular, as seen in FIG. 5B, during the course of the scanning,the robot body unit 10 thus performs the following kinds of laps betweenwall detections. The first lap comprises the robot body unit 10traversing the pool after one wall detection, aligned with the referenceorientation as described above, and keeping the corrected orientationuntil the next wall detection. This is referred to as a straight lap,designated as STR in FIG. 5B. The second lap comprises the robot bodyunit 10 traversing the pool after one wall impact, realigning itself tothe reference orientation as described above, keeping the correctedorientation for a certain period of time, and then rotating throughapproximately 90 degrees to continue moving in this orientation untilthe next wall impact. This is referred to as a stepped lap and it isdesignated as STP in FIG. 5B. Since the direction of the robot body unit10 has been altered by 90 degrees, the robot body unit 10 must alignitself accordingly subsequent to the next wall impact. Therefore,subsequent to the wall impact after the first 90 degree rotation, therobot body unit 10 realigns itself to the reference orientation plus 90degrees. Subsequent to wall impacts after successive 90 degreerotations, the robot body unit 10 alternates between realigning itselfto the reference orientation and realigning itself to the referenceorientation plus 90 degrees. In this way, it is ensured that after allwall detections, the robot body unit 10 will realign itself in twomutually perpendicular directions, whereby a Cartesian-like scanningpattern is realized, which provides a plurality of advantages comparedwith conventional non-Cartesian-like (labyrinth) patterns, forirregularly shaped pools. The increased efficiency of this method allowsthe robot to complete its cleaning cycle in less time, which may allowfor a smaller battery pack to be used.

The period of time before the rotation in each stepped lap may varydepending on the full duration of the preceding straight lap, and it mayconstitute a portion of this full duration. This portion may be chosenas small at the beginning and then increased after a predeterminednumber of wall detections have been registered. Alternatively, it may beoriginally chosen-as large and then this portion is decreased.

In particular, the time before the rotation in each stepped lap mayinitially be chosen as one half of the duration of the precedingstraight lap. This time will be reduced on each subsequent cycle by anamount which is typically less than one quarter, and can be expressed as1/n, where n is an integer. If, for example, n=8, and the duration ofthe preceding straight lap was 40 seconds, the time before rotation inthe stepped lap immediately following the straight lap is 20 seconds(one half of the duration of the straight lap). The time before rotationin each further stepped lap will be one half of the duration of itspreceding straight lap until the number of wall detections reaches apredetermined number. Then the period before rotation will become ⅜ ofthe preceding straight lap, so that if the last straight lap hadduration of 40 seconds, the robot will next rotate 15 seconds (⅜ of 40seconds) after a wall detection following a straight lap. The sameprocedure may be further repeated with the period before the rotation inthe stepped lap being decreased to ¼ and then to ⅛ of the duration ofthe preceding straight lap. This method has some advantages over thatwhere time before rotation is first small and then increases as intypical Cartesian-like scanning among which is that a user will readilysee the robot actively starting its scanning when operated.

Alternatively, the time before the rotation in each stepped lap mayinitially be any amount less than one quarter, and can be expressed astime before the retention in each stepped lap 1/n, where n is aninteger. If n=8, and the duration of the preceding straight lap was 40seconds, the time before rotation in the stepped lap immediatelyfollowing the straight lap is 5 seconds (⅛ of the duration of thestraight lap). The time before rotation in each further stepped lap willbe ⅛ of the duration of its preceding straight lap until the number ofwall detections reaches a predetermined number. Then the period beforerotation will increase, i.e. become 2/8 of the preceding straight lap,so that if the last straight lap had duration of 40 seconds, the robotwill next rotate 10 seconds ( 2/8 of 40 seconds) after a wall detectionfollowing a straight lap. The same procedure may be further repeatedwith the period before the rotation in the stepped lap being increasedto ⅜ and then to ½ of the duration of the preceding straight lap.

After a predetermined number of wall detections have occurred in eachcycle, one extra straight path may be made to make an additional walldetection prior to the increase of the period before rotation in thesubsequent stepped laps. The direction of rotation may be changed forsuch subsequent stepped laps relative to that of the previous steppedlaps.

The Cartesian-like scanning pattern as described above for arbitrarilyshaped pools, where the scanning is performed along two mutuallyperpendicular directions obtained by adjusting the robot's orientationeach time after wall impact, has appeared to be surprisingly much moreefficient than the non-Cartesian-like scanning pattern. It appears toreduce the totals by at least 30% of the scanning time for similarcoverage using a standard scanning time method.

The robot 1 may perform several additional modes for scanning thesurface of the pool floor and vertical walls.

One such mode may provide for the robot to scan the floor of the poolaccording to a given procedure, e.g. based on a labyrinth algorithm.After a predetermined period of time, the robot may ascend a verticalsidewall and scan the waterline for a predetermined period of time,after which it descends to the floor and continues scanning. The robotcan be programmed to scan according to this or any other method, at an‘intensive’ cleaning mode with the speed of the robot decreased, and thesuction increased. The robot can be programmed to perform a “wallcleaning mode” by, e.g. ascending a vertical sidewall to the waterline,cleaning the waterline for a predetermined amount of time, descendingthe sidewall to the floor, moving along the sidewall a predetermineddistance, ascending the sidewall, and continuing cleaning in the firstdirection. This cycle may be repeated a predetermined number of times,subsequent to which the robot proceeds to the next wall and continuesthe repeats the cycle there.

In order to ensure that a sidewall is always properly detected by therobot, a new method of sidewall detection is suggested. Currently, poolcleaning robots typically register sidewalls by utilizing a tilt sensor,or other mechanical device which detects when the robot begins to ascenda sidewall. The tilt sensor is typically a solid object with a tubularhollow therein. The hollow is V-shaped, with its vertex at the lowestpoint, and runs along a single plane which is parallel to gravity. Asmall sphere is disposed within the hollow, and rests, when in anon-tilted position, at the vertex. An optical sensor detects thepresence or absence of the ball. When in a tilted position along theplane, the sphere rolls away from the vertex, and a tilt is detected.This type of tilt sensor is currently used in the robot sold under thename Dolphin by Maytronics.

The tilt sensor requires that the robot begins to ascend the sidewall inorder for the tube to change position. However, in pools with verysmooth sidewalls or an algae covering on the sidewalls, the use of atilt sensor to effect a sidewall detection becomes ineffectual, and, asan alternative way suggested hereinfor, sidewall detection is based onpeak current detection. For this, the robot's main controller may bedesigned to continually monitor the current passing through the drivemotors. When the robot encounters a sidewall, the current passingthrough the drive motor increases sharply. The rise is analyzed, andwhen a threshold is reached, the main controller registers a walldetection. The threshold is determined by determining an average floorcurrent level, which may be predetermined or established at thebeginning of a cleaning cycle, as follows: the robot having both a peakcurrent detector and convention wall detection means, e.g., a tiltsensor, is allowed to traverse the pool until such a long time haspassed without a reversal due to a sidewall detection that it is assumedthat a sidewall impact has occurred, and that the impact was notdetected by the conventional means. At this point a reversal takesplace, and, after a brief period of time has passed, the controllermeasures the current passing through the drive motors. This brief periodof time is enough time for a reversal to take place, and may be on theorder of five to ten seconds. This process may be repeated several timesto obtain an average floor current value, which is then multiplied by aconstant to obtain the threshold value.

Alternatively, a robot may have the peak current detector as its solemeans of sidewall detection, at least in such cases wherein it is knownthat ascension of sidewalls is impossible. When sidewalls may beascended, the peak current detector may be used as the sole means ofsidewall detection when an appropriate threshold is predetermined.

Those skilled in the art to which this invention pertains will readilyappreciate that numerous changes, variations and modifications can beeffectuated without departing from the true spirit and scope of theinvention as defined in and by the appended claims.

1-67. (canceled)
 68. A cleaning robot adapted to move in a swimming poolor the like in accordance with commands from a main controller therein,the robot when in use being free of any cables connected to an externalpower supply, and having: (a) a body unit with a battery power pack,adapted to move along the floor and/or walls of said pool; (b) a tailunit comprising a head portion adapted to float on the surface of a pooland a connector designed for charging batteries or battery in saidbattery power pack by an external charger; and (c) a tethering cableattached at least in use, to the body unit, said tethering cable beingof sufficient length to allow the float of said head portion while thebody unit is on the floor of the pool.
 69. A cleaning robot according toclaim 68, wherein the head portion is adapted to submerge below thewater surface upon encountering an obstacle.
 70. A cleaning robotaccording to claim 68, wherein the head portion is of a geometry whichminimizes the likelihood of entanglement thereof with obstacles.
 71. Acleaning robot according to claim 68, the robot being adapted to stop ata predetermined location when a predetermined number of wall encountersoccur after the battery voltage drops below a predetermined amount. 72.A cleaning robot according to claim 68, wherein the head portioncomprises a float user interface, and is designed such that the floatuser interface is disposed at or near the surface of the pool, when thetail unit is in its working position.
 73. A cleaning robot according toclaim 72, wherein said tail unit further comprises a tail unitcontroller in communication with the main controller.
 74. A cleaningrobot according to claim 72, wherein the float user interface is adaptedto receive user input.
 75. A cleaning robot according to claim 68,wherein said tail unit further comprises at least one data presentationdevice.
 76. A cleaning robot according to claim 68, further comprisingan external battery charger, which is connectable to the tail unit forcharging at least one battery in said battery power pack in the bodyunit of the robot.
 77. A cleaning robot according to claim 76, whereinthe charger is adapted to communicate with the tail unit via a cable,and wherein another cable is used for connecting the tail unit with saidbattery power pack.
 78. A cleaning robot according to claim 76, whereinthe charger comprises at least one charger-side data presentation units.79. A cleaning robot according to claim 68, the robot having a memoryadapted to store a certain orientation of the robot, said controllerbeing adapted to provide the robot with a command to align itsorientation in accordance with the stored orientation.
 80. A cleaningrobot according to claim 79, wherein said orientation is defined by therobot's initial orientation.
 81. A cleaning robot according to claim 79,further comprising a detector for detecting a wall when impacted by therobot, wherein the alignment of the robot's orientation is performedafter at least one wall detection.
 82. A cleaning robot according toclaim 81, the robot further comprising an electro-mechanical drivemeans; said first controller being adapted to detect the current throughthe drive means, whereby when the current exceeds a threshold, thecontroller assumes a wall impact to have occurred.
 83. A cleaning robotas disclosed in claim 82, wherein the threshold is determined bymultiplying an average of the current passing through the drive meansduring one or more traversings of the pool floor by a constant.
 84. Acleaning robot according to claim 80, wherein the controller is adaptedto allow the robot to perform a straight lap and a subsequent steppedlap, each between two wall detections, both laps comprising saidalignment, the stepped lap also including rotation of the robot througha predetermined angle relative to its orientation during the straightlap, whereby the robot is adapted to move along two known mutuallyangled directions independently of the shape of the walls of theswimming pool.
 85. A cleaning robot according to claim 84, wherein saidpredetermined angle is 90 degrees.
 86. A cleaning robot according toclaim 84, wherein during the stepped lap, the robot moves for a periodconstituting a predetermined portion of the duration of the precedingstraight lap, said portion being increased after a predetermined numberof wall detections.
 87. A cleaning robot according to claim 68, adaptedto move in a swimming pool or the like, wherein the robot ispreprogrammed for performing a plurality of cleaning modes, of which atleast two are selected from a group comprising: (a) the robot scanningthe floor surface of the pool, and ascending a sidewall at predeterminedtime intervals; (b) the robot having a decreased speed and an increasedsuction; and (c) the robot executing a cycle comprising ascending asidewall to the waterline, cleaning the waterline for a predeterminedamount of time in a first direction with relation to the pool,descending the sidewall to the floor, moving along the sidewall apredetermined distance in a second direction which is opposite the firstdirection, ascending the sidewall, and continuing cleaning in the firstdirection.
 88. A cleaning robot adapted to move in a swimming pool orthe like, adapted to move in the pool along two scanning directionsobtained by adjusting the orientation of the robot in a predeterminedway relative to a reference orientation thereof, said scanningdirections having a predetermined angle therebetween, independently ofthe swimming pool's shape.
 89. A cleaning robot according to claim 88,the robot having a memory adapted to store the orientation of the robot,and a controller being adapted to provide the robot with a command toalign its orientation in accordance with the stored orientation.
 90. Acleaning robot according to claim 89, wherein said orientation isdefined by the robot's initial orientation.
 91. A cleaning robotaccording to claim 88, wherein said predetermined angle is 90 degrees.92. A cleaning robot adapted to move in a swimming pool or the like inaccordance with commands from a main controller therein, the robot whenin use being free of any cables connected to an external power supply,and having a body unit with a battery power pack, adapted to move alongthe floor and/or walls of said pool, and a tail unit comprising a headportion adapted to float on the surface of a pool, and a tethering cableattached at least in use, to the body unit; the robot comprising a meansfor detecting its orientation.
 93. A cleaning robot according to claim92, wherein the means is a digital compass integrated onto thecontroller.